**** Plot Descriptors *****************************************************

g t byt sb #b fm l p o e md <----------sf--------> <----prompt---->
<--lower--> <--upper--> <----------------title-------------->
0 0 036 00 32 00 0 0 2 0 00 8.381903171539e-8 T-02 Lat
0.000000000 0.000000000 T-02 Latitude (deg)

    g = # graphs per screen: 0 = single, 1 = double, 2 = triple
    t = graph type: 0=1 item, 1=2i, 2=3i, 3=i vs i, 4=i-constant, 5=i-i
  byt = starting byte (see below)
   bt = starting bit (fixed pt only)  : lsb = bit 0, msb = 31 (max)
   #b = number of bits (fixed pt only): 1 to 32 (max); bt + #b < 32
    l = limts: 0 = range, 1 = auto, 2 = fixed, 3 = center, 4 = relative
    p = plot mode: 0 = line mode, 1 = point mode
    o = fixed point and floating point data byte order (below)
    e = exponent: 0 = decimal limit display, 1 = exponent limit display
   md = modifier: 0=none,1=sqrt,2=dircos->lat,3=deltas with rollover,4=deltas
				  5=seg,min->deg

   fm = format (bytes):  0=fix (1-4),  1=ufix (1-4), 2=sign/mag fix (1-4)
                        10=EEEs (4), 11=EEEd (8), 12=DECs (4), 13=DECd (8),
                        14=MILs (4), 15=MILd (6), 16=C30s (4), 17=C30d (8),
                        18=CAPs (4), 19=CAPd (6)

   sf     = scale factor for item or constant for item - constant
   prompt = screen prompt to select item (not used in multi graph item)
   lower  = lower graph limit for fixed offset (l=2)
   upper  = upper graph limit for fixed offset (l=2)
   title  = title of graph on display

   The last entries in a descriptor file may be multi graph items (non
   zero g or t). When this occurs, byt, bt and #b point to other graphs
   (1st entry is 0, 2nd entry is 1, etc.) and the second line (lower,
   upper,title) is omitted.

   The "number of bits + start bit" determines how many bytes are used
   to form fixed point data:

    <  9,  1 byte           The number of bytes used must be considered
    < 17,  2 bytes          in determining byte order (below).
    < 25,  3 bytes          The number of bytes used to form floating
    else,  4 bytes          point data is predetermined.

**** Byte ordering ********************************************************

 byte order
 |
 v  1   2   3     4     6         8        <-- number of bytes
 0  a  ab  abc  abcd  abcdef  abcd efgh    correct PC order (ls byte first)
 1  a  ba  cba  dcba  fedcba  hgfe dcba    bytes are in reverse order
 2  a           cdab  efcdab  cdab ghef    word reverse
 3  a           badc  badcfe  badc fehg    byte in word reverse
 4  a                         efgh abcd    double word reverse
 5  a                         dcba hgfe    word reverse, byte in word reverse
 6  a                         fehg badc    double word rev, byte in word rev
 7  a                         ghef cdab    double word reverse, word reverse

**** Byte offsets into messages *******************************************

     NORMAL MESSAGES

     byte  1 RTtoBC   2 BCtoRT   3 RTtoRT   4 MCw/o    5 MCxmt    6 MCrec
     ----  ---------  ---------  ---------  ---------  ---------  ---------
     -02   |  TCW  |  |  RCW  |  |  RCW  |  |  TMC  |  |  TMC  |  |  RMC  |
            ---------  ---------  ---------  ---------  ---------  ---------
      00   |  LBW  |  |  DW1  |  |  TCW  |  |  LBW  |  |  LBW  |  |  DW1  |
            ---------  ---------  ---------  ---------  ---------  ---------
      02   |  MSW  |  |  DW2  |  |  LBW  |  |  MSW  |  |  MSW  |  |  LBW  |
            ---------  ---------  ---------  ---------  ---------  ---------
      04   |  DW1  |  |  DW3  |  |  MSW  |             |  DW1  |  |  MSW  |
            ---------  ---------  ---------             ---------  ---------
      06   |  DW2  |  |  DW4  |  |  DW1  |     where:
           ---------  ---------  ---------
           :       :  :       :  :       :     TCW = transmit command word
           ---------  ---------  ---------     RCW = receive  command word
     2n-2  | DWn-2 |  |  DWn  |  | DWn-3 |     TMC = tramsmit mode code
           ---------  ---------  ---------     RCW = receive  mode code
      2n   | DWn-1 |  |  LBW  |  | DWn-2 |     RBC = receive  broadcast
           ---------  ---------  ---------     TBM = transmit broadcast mode
     2n+2  |  DWN  |  |  MSW  |  | DWn-1 |     RBM = receive  broadcast mode
           ---------  ---------  ---------     MSW = mux sataus word
     2n+4                        |  DWn  |     DW  = data word
                                 ---------     LBW = loop back word
     2n+6                        |  MSW  |
                                 ---------


     BROADCAST MESSAGES

     byte  7 BCtoRTs  8 RTtoRTs  9  MCw/o   10 MCrec
     ----  ---------  ---------  ---------  ---------
     -02   |  RBC  |  |  RBC  |  |  TBM  |  |  RBC  |
           ---------  ---------  ---------  ---------
      00   |  DW1  |  |  TCW  |  |  LBW  |  |  DW1  |
           ---------  ---------  ---------  ---------
      02   |  DW2  |  |  LBW  |             |  LBW  |
           ---------  ---------             ---------
      04   |  DW3  |  |  MSW  |      Note:
           ---------  ---------
      06   |  DW4  |  |  DW1  |      The 1553 interface card deposits 16
           ---------  ---------      bit data into memory in the correct
           :       :  :       :      PC order, lsbs 1st (even byte).
           ---------  ---------
     2n-2  |  DWn  |  | DWn-3 |      UUT 32 bit data is deposited MSH then
           ---------  ---------      LSH, which is PC word backward. The
      2n   |  LBW  |  | DWn-2 |      data reduction routines swap the
           ---------  ---------      2 words for items > 16 bits.
     2n+2             | DWn-1 |
                      ---------
     2n+4             |  DWn  |
                      ---------
